NASHVILLE, Tenn. (AP) — Republican Sen. Lamar Alexander, a 40-year veteran of Tennessee politics, is facing a challenge Thursday from two tea party-styled candidates who have tried to cast him as out of touch with the state's increasingly conservative electorate.

Should state Rep. Joe Carr or Memphis radio station owner George Flinn prevail against Alexander on Thursday, they would be the first challenger to knock off an incumbent U.S. senator in this year's midterm elections. So far this year, the argument that sitting senators have lost their connection with voters hasn't been a winner.

In Kentucky, the ultimate Senate insider, Minority Leader Mitch McConnell, had no trouble holding back tea party challenger Matt Bevin. It took a runoff to do it, but Sen. Thad Cochran also beat back an effort from state lawmaker Chris McDaniel to "primary" him in Mississippi.

The latest win for a Senate incumbent, and failure for the "insider" argument, came Tuesday when Kansas GOP Sen. Pat Roberts outpaced radiologist Milton Wolf. Roberts survived despite telling a radio interviewer last month: "Every time I get an opponent — uh, I mean, every time I get a chance — I'm home."

Alexander sought to avoid any chance Carr or Flinn could make that case against him by locking down key endorsements early. He's spent the final few weeks of the campaign on a 35-stop bus tour around the state stressing his ability to get results in a divided Senate.

Alexander, 74, has served two terms as the state's governor and two terms in the Senate. He has outspent Carr by a ratio of five-to-one through the most recent campaign finance disclosures, but Carr said voter unrest over issues like immigration should be enough to make up for his vast disadvantage in fundraising.

Also on the Tennessee ballot Thursday is embattled Republican Rep. Scott DesJarlais, a physician from the small south Tennessee town of Jasper who won re-election in 2012 despite revelations that he once urged a patient he was dating to seek an abortion.

After the election, court officials released transcripts of divorce proceedings that included DesJarlais admitting under oath that he had eight affairs, encouraged a lover to get an abortion and used a gun to intimidate his first wife during an argument.

Last year, DesJarlais was reprimanded and fined by the Tennessee Board of Medical Examiners in May for having sex with patients. But the congressman has since doubled down on his tea party credentials and has dismissed the details about his personal life as "old news." He faces state Sen. Jim Tracy, who has far outraised the incumbent.

Other contested congressional primaries include the latest primary challenge to Democratic Rep. Steve Cohen, a white and Jewish Memphis native, in the state's majority black 9th Congressional District. Challenger Ricky Wilkins, an attorney and African American, has sought to highlight ethnic and racial differences between Cohen and his constituents in the district, which Cohen has represented since 2006.